1. Field of the Invention
The present invention relates to a power supply device and, more particularly, to a power supply device for driving a light emitting diode (LED) capable of controlling the switching of multiple output powers, in synchronization with the frequency of one of the multiple output powers and simplifying a power conversion stage in supplying power for driving an LED.
2. Description of the Related Art
A power supply device has been widely used for information devices such as a personal computer, and the like, and home appliances such as an air-conditioner, an audio system, a visual device, and the like.
The power supply device may provide a plurality of output powers depending on the electronic devices to which the power supply device is applied.
A general multi-power source supply device converts an input DC power into an AC power through a single transformer and then rectifies the converted AC power, respectively, to output a plurality of DC powers. However, the general multi-power source supply device has a problem in that when a voltage level of a single DC power, among the plurality of DC powers, is changed by the single transformer, the remaining DC powers are affected, so cross-regulation is therefore not maintained. To solve this problem, a step-down chopper circuit (or a buck chopper circuit) is employed at an output stage, but re-conversion of power by the step-down chopper circuit after a primary power conversion degrades power conversion efficiency and the presence of the step-down chopper circuit increases the number of components, resulting in an increase in fabrication costs.
In addition, when the power supply device is employed to drive LEDs, a boost circuit (or a voltage step-up circuit) or a buck circuit (or a voltage step-down circuit) is required to compensate for a voltage deviation among the LEDs after the primary power conversion, which also degrades power conversion efficiency and increases the number of required components, thereby increasing fabrication costs.